Introduce a yaml_utils.Walk function

pkg/utils/yaml_utils/yaml_utils.go

@@ -153,3 +153,74 @@ func renameYamlKey(node *yaml.Node, path []string, newKey string) (bool, error)
 
 	return renameYamlKey(valueNode, path[1:], newKey)
 }
+
+// Traverses a yaml document, calling the callback function for each node. The
+// callback is allowed to modify the node in place, in which case it should
+// return true. The function returns the original yaml document if none of the
+// callbacks returned true, and the modified document otherwise.
+func Walk(yamlBytes []byte, callback func(node *yaml.Node, path string) bool) ([]byte, error) {
+	// Parse the YAML file.
+	var node yaml.Node
+	err := yaml.Unmarshal(yamlBytes, &node)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse YAML: %w", err)
+	}
+
+	// Empty document: nothing to do.
+	if len(node.Content) == 0 {
+		return yamlBytes, nil
+	}
+
+	body := node.Content[0]
+
+	if didChange, err := walk(body, "", callback); err != nil || !didChange {
+		return yamlBytes, err
+	}
+
+	// Convert the updated YAML node back to YAML bytes.
+	updatedYAMLBytes, err := yaml.Marshal(body)
+	if err != nil {
+		return nil, fmt.Errorf("failed to convert YAML node to bytes: %w", err)
+	}
+
+	return updatedYAMLBytes, nil
+}
+
+func walk(node *yaml.Node, path string, callback func(*yaml.Node, string) bool) (bool, error) {
+	didChange := callback(node, path)
+	switch node.Kind {
+	case yaml.DocumentNode:
+		return false, fmt.Errorf("Unexpected document node in the middle of a yaml tree")
+	case yaml.MappingNode:
+		for i := 0; i < len(node.Content); i += 2 {
+			name := node.Content[i].Value
+			childNode := node.Content[i+1]
+			var childPath string
+			if path == "" {
+				childPath = name
+			} else {
+				childPath = fmt.Sprintf("%s.%s", path, name)
+			}
+			didChangeChild, err := walk(childNode, childPath, callback)
+			if err != nil {
+				return false, err
+			}
+			didChange = didChange || didChangeChild
+		}
+	case yaml.SequenceNode:
+		for i := 0; i < len(node.Content); i++ {
+			childPath := fmt.Sprintf("%s[%d]", path, i)
+			didChangeChild, err := walk(node.Content[i], childPath, callback)
+			if err != nil {
+				return false, err
+			}
+			didChange = didChange || didChangeChild
+		}
+	case yaml.ScalarNode:
+		// nothing to do
+	case yaml.AliasNode:
+		return false, fmt.Errorf("Alias nodes are not supported")
+	}
+
+	return didChange, nil
+}

pkg/utils/yaml_utils/yaml_utils_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"gopkg.in/yaml.v3"
 )
 
 func TestUpdateYamlValue(t *testing.T) {
@@ -199,3 +200,82 @@ func TestRenameYamlKey(t *testing.T) {
 		})
 	}
 }
+
+func TestWalk_paths(t *testing.T) {
+	tests := []struct {
+		name          string
+		document      string
+		expectedPaths []string
+	}{
+		{
+			name:          "empty document",
+			document:      "",
+			expectedPaths: []string{},
+		},
+		{
+			name:          "scalar",
+			document:      "x: 5",
+			expectedPaths: []string{"", "x"}, // called with an empty path for the root node
+		},
+		{
+			name:          "nested",
+			document:      "foo:\n  x: 5",
+			expectedPaths: []string{"", "foo", "foo.x"},
+		},
+		{
+			name:          "array",
+			document:      "foo:\n  bar: [3, 7]",
+			expectedPaths: []string{"", "foo", "foo.bar", "foo.bar[0]", "foo.bar[1]"},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			paths := []string{}
+			_, err := Walk([]byte(test.document), func(node *yaml.Node, path string) bool {
+				paths = append(paths, path)
+				return true
+			})
+
+			assert.NoError(t, err)
+			assert.Equal(t, test.expectedPaths, paths)
+		})
+	}
+}
+
+func TestWalk_inPlaceChanges(t *testing.T) {
+	tests := []struct {
+		name        string
+		in          string
+		callback    func(node *yaml.Node, path string) bool
+		expectedOut string
+	}{
+		{
+			name:        "no change",
+			in:          "x: 5",
+			callback:    func(node *yaml.Node, path string) bool { return false },
+			expectedOut: "x: 5",
+		},
+		{
+			name: "change value",
+			in:   "x: 5\ny: 3",
+			callback: func(node *yaml.Node, path string) bool {
+				if path == "x" {
+					node.Value = "7"
+					return true
+				}
+				return false
+			},
+			expectedOut: "x: 7\ny: 3\n",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			result, err := Walk([]byte(test.in), test.callback)
+
+			assert.NoError(t, err)
+			assert.Equal(t, test.expectedOut, string(result))
+		})
+	}
+}